1. Field of the Invention
This invention relates to a silicone coated base material having a silicone coating formed on a base material. It also relates to an air bag base material.
2. Prior Art
Most of coating compositions used for automotive air bags in the prior art are chloroprene resin blends. The chloroprene resin blends are also used in treating fibrous base materials in the form of woven, knitted and non-woven fabrics of polyamide fibers as by impregnation, coating or lamination. The resulting composite materials have excellent properties inherent to both the polyamide fibers and chloroprene resin and are useful in a variety of applications.
However, these composite materials have some drawbacks. They tend to gradually lose their strength when they are allowed to stand above a certain temperature over a long term because the chloroprene resin releases hydrogen chloride which acts to scissor amide bonds of the polyamide fibers. Since the chloroprene resin is relatively hard, the resin excessively restrains polyamide fibers of the fibrous base material in the composite material, preventing free motion of the fibers. Thus, the composite materials have a relatively hard feel or suitability and low tear strength.
To overcome these drawbacks, it was proposed to use coating compositions mainly comprising silicone resins which are superior to the chloroprene resins with respect to heat resistance, weathering, and flexibility. Typical known compositions are blends of a heat vulcanizable silicone resin and a tackifier and blends of an addition-curing type silicone rubber and a tackifier. These silicone coating compositions are applied to base materials of air bags, particularly for automobiles or the like to form coatings thereon which are generally about 40 .mu.m thick. However, to meet a market demand for light weight, compact and low cost products, it is desirable to reduce the coating thickness.
As the coating thickness is reduced, the conventional coating compositions tend to increase in burn rate. When they are applied to air bags for such as automobiles, thin coatings permit the air bags to puncture upon explosive expansion of an inflator. As a result, the air bags lose air tightness and are thus impractical.